The present invention relates to an apparatus and method for the magnetic alignment of an imaging subsystem having linear translation-bearing rods.
Pre-press proofing is a procedure that is used by the printing industry for creating representative images of printed material without the high cost and time that is required to actually produce printing plates and set up a high-speed, high volume, printing press to produce an example of an intended image. An image may require several corrections and be reproduced several times to satisfy or meet the customers requirements resulting in loss of profits and ultimately higher costs to the customer.
One such commercially available image processing apparatus is arranged to form an intended image on a sheet of print media. Colorant is transferred from a sheet of donor material to print media to form the intended image. This image processing apparatus generally includes a material supply assembly or carousel, and a lathe bed scanning subsystem or write engine, which includes a lathe bed scanning frame, translation drive, translation stage member, printhead, load roller, and imaging drum, and print media and donor material transports.
The printhead is mounted on the movable translation stage member, which is supported on translation-bearing rods. The linear translation subsystem includes the translation stage member, the translation-bearing rods, and the translator drive. The front translation-bearing rod locates the translation stage member in the vertical and the horizontal directions with respect to axis X of the imaging drum. The rear translation-bearing rod locates the translation stage member only with respect to rotation of the translation stage member about the front translation-bearing rod. The translator drive traverses the translation stage member and printhead axially along the imaging drum.
The translation subsystem also includes the lead screw subassembly. The lead screw includes an elongated, threaded shaft, which is attached to the translator linear drive motor on its drive end and to the lathe bed scanning frame by means of a radial bearing. A lead screw drive nut includes grooves in its hollowed-out center portion for mating with the threads of the threaded shaft. This allows the lead screw drive nut axial movement along the threaded shaft as the threaded shaft is rotated by the linear drive motor. The lead screw drive nut is integrally attached to the printhead through the lead screw coupling and the translation stage member at its periphery, so that the threaded shaft is rotated by the linear drive motor. This moves the lead screw drive nut axially along the threaded shaft, which in turn moves the translation stage member, and ultimately the printhead axially along the imaging drum. The printhead travels in a path along the drum.
Although the presently known and utilized image processing (or imaging) apparatus is satisfactory, it is not without drawbacks. Drawbacks include the following. First, misalignment of the linear translation subsystem limits output quality. Image quality of the intended image, intended image to intended image, and the intended image from imaging apparatus to imaging apparatus suffers when the imaging subsystem is mis-aligned. Also, the intended image, intended image to intended image within a given imaging apparatus, or intended image to intended image from one imaging apparatus to another imaging apparatus may differ. The same is true of the alignment of the printhead to the imaging drum surface or the print media and colorant donor material. With existing imaging (or image processing) apparatus, alignment of the linear translation subsystem, and the printhead relative to the imaging drum surface or the print media and colorant donor material, is limited by the constraints imposed by currently available manufacturing technology.
For example, currently available image processing apparatus have fixed translation-bearing rods, which, even though they may fall within manufacturing specifications, are often very slightly bowed. Even a slight bowing can interfere with the performance of the image processing system containing the bowed translation-bearing rod or rods.
The present invention reduces or eliminates reliance on tight manufacturing tolerances for translation-bearing rods by pre-aligning the linear translation subsystem prior to use of the image processing apparatus containing the linear translation subsystem. Once the aligning process of the present invention has been conducted, it is not necessary to re-align the imaging subsystem for many years.
Advantages of the present invention include the following. First, the aligned linear translation subsystem of the imaging subsystem provides an increase in image quality of the intended image, intended image to intended image, and the intended image from imaging apparatus to imaging apparatus. Second, the need to automatically focus the printhead is reduced or eliminated by improved alignment of the linear translation subsystem and printhead to the imaging drum surface, and also to the print media and the colorant donor material. Third, the linear translation subsystem is aligned, as is the printhead to the imaging drum surface, print media, and colorant donor material. This considerably reduces final costs and required maintenance of the imaging apparatus. Finally, the present invention provides an added margin for depth of focus, and for handling a larger range of media thickness tolerances.
The present invention includes an accurate system for magnetic alignment of an imaging subsystem, including:
1) a master alignment fixture, including: a) two like, magnet-attracting translation-bearing rods; b) a drum axis tool or drum; c) a means for supporting the translation-bearing rods in a parallel, planar relationship to one another; d) a means for supporting the drum axis tool or drum in a parallel relationship to the translation-bearing rods; and e) a means for measuring and aligning the translation-bearing rods in relation to the parallel drum axis tool or drum; and
2) a removable set apparatus that is attachable to the top of the master alignment fixture, including: a) a tube or rod; b) a plurality of aligned first set arms extending in a downward direction from the tube or rod, at least one magnet being attached to each first set arm, the first set arms being above and in close proximity to the translation-bearing rods when the set apparatus is on the master alignment fixture, the magnets of the first set arms being detachably attachable to the translation-bearing rod; and c) at least two second, extended arms projecting from a side of the tube or rod, the second, extended arms being detachably attachable to the drum axis tool or drum.
The present invention also includes a process for magnetically aligning an imaging subsystem, comprising the steps of:
a) mounting one or two translation-bearing rods, and a drum axis tool or a drum, in a master alignment fixture;
b) placing a removable set apparatus over the master alignment fixture, thereby removably attaching at least two loosely set magnets on at least one, first pair of arms of the set apparatus to the translation-bearing rods, and at least two magnets on a second, extended pair of arms of the set apparatus to the drum axis tool or drum;
c) adjusting the translation-bearing rods relative to the drum axis tool or drum;
d) fixing the translation-bearing rod magnets on the set apparatus in their adjusted positions;
e) removing the set apparatus from the master alignment fixture; and
f) inserting the set apparatus in an imaging subsystem of an image processing apparatus for aligning the imaging subsystem.